1. Field of the Invention
Apparatuses and methods consistent with the present invention relate to transmitting/receiving radio frequency (RF) signals, and more particularly, to reducing a direct current (DC) offset due to a phase noise and reducing a gain linearity by removing a leakage component in a received signal.
2. Description of Related Art
A transceiver transmitting/receiving an RF signal is utilized in a system for transmitting/receiving high speed wireless data, such as a mobile phone, a digital multimedia broadcasting (DMB) phone, and a personal digital assistant (PDA). A transmitter transmits data by including the data in a predetermined carrier signal. A receiver extracts data by processing a received RF signal. Presently, the development of a transceiver, which can be miniaturized with low power consumption even in a ubiquitous system of a multi-band orthogonal frequency division multiplexing ultra-wide band standard (MB-OFDM UWB), is an important issue in the design and implementation of various types of portable systems. FIG. 1 is a diagram illustrating a conventional RF receiver 100. Referring to FIG. 1, the RF receiver 100 includes an in-phase mixer (I-mixer) 110, a quadrature-phase mixer (Q-mixer) 130, low pass filters (LPFs) 120 and 140, and a demodulator 150.
The I-mixer 110 multiplies and frequency-down converts a received RF signal RXIN and a local signal LOI. In this instance, a signal obtained by the multiplication is processed in the LPF 120 and an output of the LPF 120 is input into the demodulator 150. The Q-mixer 130 multiplies and frequency-down converts the RF signal RXIN and a Q signal, LOQ, of the local signal LOI. In this instance, the signal obtained by the multiplication is processed in the LPF 140 and an output of the LPF 140 is input into the demodulator 150. The demodulator 150 demodulates the outputs of the LPFs 120 and 140 according to algorithms such as phase shift keying (PSK), quadrature phase shift keying (QPSK) and amplitude shift keying (ASK), and obtains certain information contained in the signal that is demodulated. The demodulated signal may be further processed in a post processor. Also, the demodulated signal may then be indicated as information that a user can recognize, via an audio output device or display, such as a mobile phone, a DMB phone, a PDA, and a radio frequency identification (RFID) reader.
The conventional RF receiver 100 may receive a noise component with the RF signal RXIN. The demodulator 150 has a complex task of removing effects, such as gain saturation, a DC offset, and phase variation of a received RF signal caused by a noise component. The aforementioned complex task of the demodulator 150 for improving a signal-to-noise ratio (SNR) of a received signal may increase a circuit complexity and power consumption. Also, the received noise component described above may be introduced from a directional coupler (DCPLR), which is utilized in a transceiver of a general full-duplex communication method. As an example, a transceiver of a system such as an RFID tag reader transmits/receives an RF signal via one antenna. In this case, leakage of an RF signal that is transmitted may be introduced into an RF signal that is received by a DCPLR that connects transmitting and receiving paths.